You asked about BMI training and management styles
I spent over twenty years working for BMI mainly as a captain and as you would expect they seemed to me to be about average for the industry overall. The whole thing is held together by Sir Michael who has an amazing grip of the industry and steers his company remoetly. I never met a manager who had a management qualification indeed such would have been seen as very suspect. Managers generally stuck to the hard man approach and frequently seemed to use a what can we get away with rather than what is fair method of decision making. They frequently seemed to spend more time concealing or polishing their activities for the benefit of other managers rather than doing their stated jobs.
Training is excellent once away from the conversion centre which uses a weird second party training firm in their own training centre for initial training but BMI training captains thereafter
Terms and conditions were excellent but have been drawn back rather recently with pension changes and the like
Overall you could do much worse for a long term decision but if you can get BA or Virgin do